--- a/graal/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/GuardsTest.java	Fri Aug 30 17:45:53 2013 +0200
+++ b/graal/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/GuardsTest.java	Mon Sep 02 15:22:25 2013 +0200
@@ -34,11 +34,15 @@
 import com.oracle.truffle.api.dsl.test.GuardsTestFactory.GuardWithBoxedPrimitiveFactory;
 import com.oracle.truffle.api.dsl.test.GuardsTestFactory.GuardWithObjectFactory;
 import com.oracle.truffle.api.dsl.test.GuardsTestFactory.InvocationGuardFactory;
+import com.oracle.truffle.api.dsl.test.GuardsTestFactory.TestAbstractGuard1Factory;
 import com.oracle.truffle.api.dsl.test.GuardsTestFactory.TestGuardResolve1Factory;
 import com.oracle.truffle.api.dsl.test.GuardsTestFactory.TestGuardResolve2Factory;
 import com.oracle.truffle.api.dsl.test.GuardsTestFactory.TestGuardResolve3Factory;
 import com.oracle.truffle.api.dsl.test.NodeContainerTest.Str;
 import com.oracle.truffle.api.dsl.test.NodeContainerTest.StrBase;
+import com.oracle.truffle.api.dsl.test.TypeSystemTest.Abstract;
+import com.oracle.truffle.api.dsl.test.TypeSystemTest.BExtendsAbstract;
+import com.oracle.truffle.api.dsl.test.TypeSystemTest.CExtendsAbstract;
 import com.oracle.truffle.api.dsl.test.TypeSystemTest.TestRootNode;
 import com.oracle.truffle.api.dsl.test.TypeSystemTest.ValueNode;
 
@@ -271,4 +275,43 @@
         }
     }
 
+    @NodeChild("expression")
+    public abstract static class TestGuardResolve4 extends ValueNode {
+
+        boolean guard(StrBase primitive) {
+            return false;
+        }
+
+        @Specialization(guards = "guard")
+        int doSpecialized(Str value0) {
+            return 42;
+        }
+    }
+
+    @Test
+    public void testAbstractGuard1() {
+        TestRootNode<?> root = createRoot(TestAbstractGuard1Factory.getInstance());
+
+        assertEquals(BExtendsAbstract.INSTANCE, executeWith(root, BExtendsAbstract.INSTANCE));
+        assertEquals(CExtendsAbstract.INSTANCE, executeWith(root, CExtendsAbstract.INSTANCE));
+    }
+
+    @NodeChild("expression")
+    public abstract static class TestAbstractGuard1 extends ValueNode {
+
+        boolean guard(Abstract value0) {
+            return true;
+        }
+
+        @Specialization(order = 1, guards = "guard")
+        BExtendsAbstract doSpecialized1(BExtendsAbstract value0) {
+            return value0;
+        }
+
+        @Specialization(order = 2, guards = "guard")
+        CExtendsAbstract doSpecialized2(CExtendsAbstract value0) {
+            return value0;
+        }
+    }
+
 }

--- a/graal/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/TypeSystemTest.java	Fri Aug 30 17:45:53 2013 +0200
+++ b/graal/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/TypeSystemTest.java	Mon Sep 02 15:22:25 2013 +0200
@@ -30,7 +30,7 @@
 
 public class TypeSystemTest {
 
-    @TypeSystem({int.class, boolean.class, String.class, Str.class, CallTarget.class, Object[].class})
+    @TypeSystem({int.class, boolean.class, String.class, Str.class, CallTarget.class, BExtendsAbstract.class, CExtendsAbstract.class, Abstract.class, Object[].class})
     static class SimpleTypes {
 
         static int intCheck;
@@ -73,6 +73,14 @@
             return SimpleTypesGen.SIMPLETYPES.expectObjectArray(execute(frame));
         }
 
+        public BExtendsAbstract executeBExtendsAbstract(VirtualFrame frame) throws UnexpectedResultException {
+            return SimpleTypesGen.SIMPLETYPES.expectBExtendsAbstract(execute(frame));
+        }
+
+        public CExtendsAbstract executeCExtendsAbstract(VirtualFrame frame) throws UnexpectedResultException {
+            return SimpleTypesGen.SIMPLETYPES.expectCExtendsAbstract(execute(frame));
+        }
+
         public abstract Object execute(VirtualFrame frame);
 
         @Override
@@ -154,4 +162,18 @@
 
     }
 
+    abstract static class Abstract {
+    }
+
+    static final class BExtendsAbstract extends Abstract {
+
+        static final BExtendsAbstract INSTANCE = new BExtendsAbstract();
+
+    }
+
+    static final class CExtendsAbstract extends Abstract {
+
+        static final CExtendsAbstract INSTANCE = new CExtendsAbstract();
+    }
+
 }

--- a/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/node/SpecializationGroup.java	Fri Aug 30 17:45:53 2013 +0200
+++ b/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/node/SpecializationGroup.java	Mon Sep 02 15:22:25 2013 +0200
@@ -119,6 +119,11 @@
         if (previous == null || previous.getGuards().size() != elseConnectedGuards.size() + 1) {
             return null;
         }
+
+        if (elseConnectedGuards.contains(guard)) {
+            return guard;
+        }
+
         GuardData previousGuard = previous.getGuards().get(elseConnectedGuards.size());
         if (guard.getMethod().equals(previousGuard.getMethod()) && guard.isNegated() != previousGuard.isNegated()) {
             return guard;
@@ -212,7 +217,7 @@
             int signatureIndex = 0;
             for (ActualParameter parameter : guardMatch.getParameters()) {
                 signatureIndex++;
-                if (parameter.getSpecification().isSignature()) {
+                if (!parameter.getSpecification().isSignature()) {
                     continue;
                 }